1. Field of Invention
The present invention relates to a manufacturing method for a substrate device having a bonding interface on a substrate of an SOI (Silicon On Insulator) structure, as well as such a substrate device. The invention also relates to a manufacturing method for an electrooptical apparatus including a liquid-crystal device having a substrate device, as well as such an electrooptical device. The invention further relates to an electronic appliance having such an electrooptical device.
2. Description of Related Art
It is a general practice to manufacture an SOI-structured substrate device, which is one example of a substrate device having a bonding interface on a substrate thereof. An insulating film is formed on the surface of a main substrate, on one hand. On the other hand, an insulating film is formed on the surface of a semiconductor substrate that is separately prepared. Then, both substrates, in a state that they are closely contacted at the insulating films, are thermally processed to bond the insulating films together. Thereafter, the semiconductor substrate is separated so that a predetermined film thickness of a single-crystal semiconductor layer that is close to the bonding interface is left on the main substrate. This provides an SOI structure having these insulating films on the main substrate on which a single-crystal semiconductor layer is further formed. Thereafter, the thus formed single-crystal semiconductor layer is used to fabricate, thereon, semiconductor elements of thin film transistors (hereinafter xe2x80x9cTFTsxe2x80x9d), thin-film diodes (hereinafter xe2x80x9cTFDsxe2x80x9d) and the like, thereby completing a substrate device.
With such a bonding technique, it is possible to form, on the substrate, high-performance semiconductor elements including a single-crystal semiconductor layer provided on a transparent substrate, e.g., a quartz glass substrate or a glass substrate, and to also form this structure on a semiconductor substrate.
However, in accordance with the above method, there is a tendency that the structure becomes complicated and that the thickness of the structure increases. For example, where an electrooptical device, such as a liquid-crystal device, is manufactured by using this type of substrate device, there is a need to form the layers of a light shielding film and interconnections at a position beneath the single-crystal semiconductor layer as well as above it. Particularly, there arises a necessity to electrically connect the light shielding film or interconnection and the other interconnection or element formed in the layers over the single-crystal semiconductor layer. In such a case, it is required to open a contact hole penetrating the interface between the insulating films. According to the research by the present inventor, where a contact hole penetrating such a bonding interface is opened simply by etching, an etch solution intrudes to the bonding interface. This may cause cracks or strip at a point in the contact hole passing the bonding interface, irregularly broadening in the bonding-interface gap in a direction along the substrate surface, poor electrical connection or insulation due to the contact hole, or poor electrical connection and insulation in the other interconnections and elements positioned close to the contact hole, for example.
As described above, the SOI or bonding technique per se that is generally used in the manufacturing method for a semiconductor device is advantageous. However, where this method is applied to a comparatively complicated overlying structure and particularly requiring a contact hole penetrating a bonding interface, as in the substrate device for an electrooptical device, such as a liquid-crystal device, defects, such as cracks and strip, may occur at the point in the contact hole passing the bonding interface. Thus, a serious malfunction in the device may be eventually incurred, which reduces the manufacturing yield.
The present invention addresses the foregoing problem, and provides a manufacturing method for a substrate device and such a substrate device capable, where manufacturing a substrate device requiring an open contact hole penetrating a bonding interface, of causing less defects at the point in the contact hole passing the bonding interface to finally enhance device reliability and thus manufacturing yield. The invention also provides a manufacturing method for an electrooptical device including the manufacturing method for a substrate device, such an electrooptical device, and an electronic appliance having such an electrooptical device.
A method for manufacturing a substrate device of the present invention that addresses the foregoing problem. The substrate device includes, on a substrate, a first conductive film, a first insulating film formed overlying the first conductive film, a second insulating film bonded on the first insulating film, a second conductive film overlying the second insulating film, and a contact hole opened in the first and second insulating films to connect the first conductive film and the second conductive film, and penetrate a bonding interface between the first insulating film and the second insulating film. The method includes a bonding step of bonding the first insulating film and the second insulating film together; an etching step of opening the contact hole penetrating the bonding interface by etching after the bonding step; a connecting step of electrically connecting between the first conductive film and the second conductive film through the contact hole. The etching process is made by dry etching that is started at least before an etchant reaches the bonding interface.
According to the method for manufacturing a substrate device of the invention, at first the first insulating film and the second insulating film are bonded together, for example, by a thermal process or the like in the bonding process. Thereafter, in the etching process, a contact hole is opened by etching that penetrates the bonding interface. On this occasion, dry etching is conducted at least before an etchant reaches the bonding interface. Thereafter, in the connection process, the first conductive film and the second conductive film are electrically connected through the contact hole. Consequently, electrical connection is provided, through the contact hole extending perpendicular to a substrate surface, between the interconnection, electrode, element or the like formed by the first conductive film and the interconnection, electrode, element or the like formed by the second conductive film, that are formed in the films sandwiching the bonding interface. Particularly, because the etching process to open a contact hole is made by dry etching that is high in directivity by the use of an etching gas at least before the etchant reaches the bonding interface, there is no possibility that the etch solution intrude to the bonding interface as encountered in wet etching. As a result, there is a reduced or almost no possibility that cracks or strip occur in a point of the contact hole passing the bonding interface or irregularly broadening in the gap at the bonding interface in a direction along the substrate surface. Accordingly, reliable electrical connection is available by the contact hole. Furthermore, reliable electrical connection or insulation is available in the other interconnection, element or the like that is positioned close to that contact hole.
As a result of the above, where the bonding technique is applied to the application requiring such a contact hole as having a comparatively complicated overlying structure and penetrating particularly a bonding interface, as in the substrate device for an electrooptical device, such as a liquid-crystal device, defects can be reduced at the point of the contact hole passing the bonding interface. This ultimately conspicuously enhances device reliability and manufacturing yield of the substrate device.
In one form of a method for manufacturing a substrate device of the invention, the substrate device further includes a semiconductor layer that is formed on the second insulating film and an interlayer insulating film that is formed on the semiconductor layer, the second conductive film being formed on the interlayer insulating film over the substrate. The method includes, before the bonding step, a step of forming the first conductive film on the substrate, a step of forming the first insulating film on the first conductive film, and a step of forming the second insulating film on the semiconductor layer included in a vicinity of a surface of a semiconductor substrate that is prepared separately from the substrate; and after the bonding step, a step of separating the semiconductor layer from the semiconductor substrate so that the second insulating film and the semiconductor layer are left on the first insulating film.
According to this form, prior to the bonding process, a first conductive film is formed on the substrate to form a first insulating film on the first conductive film, on one hand. On the other hand, a second insulating film is formed on a semiconductor layer included in the vicinity of the surface of the semiconductor substrate. After the bonding process, the semiconductor layer is separated from the semiconductor substrate so that the second insulating film and the semiconductor layer are left on the first insulating film. Accordingly, it is possible to manufacture, by the bonding technique, a substrate device having an interconnection, electrode, element or the like that is formed by a second conductive film overlying the semiconductor layer through an interlayer insulating film.
In accordance with a form of the invention, the semiconductor layer that is separated may be a single-crystal silicon layer.
This manufacturing method provides an SOI structure having a single-crystal silicon layer formed on a transparent substrate of a glass substrate, quartz substrate or the like, instead of a semiconductor substrate.
In accordance with a form of the invention, the step of separating the semiconductor layer further includes a step of fabricating a channel region, a source region and a drain region in the semiconductor layer to form a thin film transistor, and a step of forming the interlayer insulating film on the thin film transistor. The etching step opens the contact hole to penetrate through the interlayer insulating film, the second insulating film and the first insulating film.
With this manufacturing method, high-performance thin film transistors can be formed having, as a semiconductor layer, a single-crystal silicon layer on the SOI substrate. Moreover, a reliable substrate device can be manufactured having electrical connection through the contact hole between the second conductive film of interconnection, electrode, element or the like positioned above the thin film transistor and the first conductive film of interconnection, electrode, element or the like positioned below the thin film transistor.
In this case, the step of forming the first conductive film may include forming the first conductive film by a conductive light shielding film in a region of the semiconductor layer opposed at least to the channel region on the substrate.
With this manufacturing method, in the case of using a transparent substrate as a substrate, a substrate device can be manufactured which can favorably perform light shielding of the incident light on the channel region of the thin film transistor from the side of substrate by shielding the first conductive film during the manufacture of the device. Consequently, the characteristic of the thin film transistor can be further enhanced by reducing or preventing light-leak current due to a photoelectric effect in the channel region during operation. Incidentally, such a shielding conductive film may be formed by a single metal, an alloy, a metal silicide, a polycide or a lamination thereof, including at least one of refractory metals, e.g., Ti (titanium), Cr (chromium), W (tungsten), Ta (tantalum) and Mo (molybdenum).
The foregoing form, including a step of forming a thin film transistor may further include, on the substrate, a step of of forming a source electrode connected to the source region by reducing a resistance of a silicon film due to ion implantation, and a step of of forming a drain electrode connected to the drain region by reducing a resistance of a silicon film due to ion implantation.
With this manufacturing method, the source or drain electrode formed by a silicon film reduced in resistance by ion implantation can be favorably connected to a source or drain region formed, e.g., by a single-crystal silicon or polysilicon film. In this case, particularly where the source or drain region is a P+ type, the formation of a P+-type source or drain electrode by ion implantation does not require the architecture of a PN junction in the junction surface of the both, thus realizing favorable electrical connection.
In this case, the source electrode and the drain electrode may be formed by the same layer as the second conductive film.
With this manufacturing method, using the same layer as the second conductive film, the overlying structure and the manufacture process are simplified on the substrate.
Another form of a method for manufacturing a substrate device of the invention further includes a step of performing a CMP (Chemical Mechanical Polishing) process on the first insulating film prior to the bonding step.
According to this form, because the bonding process is performed after planarizing the first insulating film by a CMP process, the gap can be decreased at the bonding interface between the first insulating film and the second insulating film. Incidentally, the second insulating film, if formed by thermal oxidation on the semiconductor substrate, can obtain sufficient flatness. This also can be CMP-processed.
In another form of a method for manufacturing a substrate device of the invention, in the bonding step, the first insulating film and the second insulating film are bonded together in a close contact state by a thermal process.
With this form, bonding is comparatively easy to perform by a thermal process, e.g., at approximately 600xc2x0 C.
In another form of a method for manufacturing a substrate device of the invention, the etching process is performed without using wet etching.
With this form, because a contact hole is opened, extending from the second conductive film to the first conductive film, by only dry etching without using wet etching, the etching process is performed comparatively simply.
In another form of a method for manufacturing a substrate device of the invention, the etching step is performed by wet etching at least temporarily until an etchant reaches the bonding interface, followed by dry etching.
In accordance with this form, in the etching process, wet etching is performed at least temporarily until the etchant reaches the bonding interface. Namely, wet etching is performed using an etch solution down to a predetermined depth shallower than the bonding interface, by etching-time control or the like. Thereafter, dry etching is performed to continue etching penetrating the bonding interface to the first conductive film. Accordingly, the etch solution will not intrude to the bonding interface.
In another form of a method for manufacturing a substrate device of the invention, in the connecting step, a part of the second conductive film is formed at an inside of the contact hole.
In accordance ith this form, after opening a contact hole, where forming a second conductive film, e.g., by sputtering, CVD or the like, a part of second conductive film is also formed in the contact hole. This comparatively easily provides a structure having the integral connection between the interconnection, electrode, element or the like formed by a second conductive film having a predetermined pattern and a portion of the second conductive film at the inside of the contact hole.
In another form of a method for manufacturing a substrate device of the invention, in the connecting step, a conductive plug is formed at an inside of the contact hole.
In accordance with this form, after opening a contact hole, a conductive plug, e.g., of a refractory metal, is formed in the contact hole. Even if the contact hole has a great depth or small in diameter, electrical connection that is comparatively high in reliability is obtained through the contact hole.
A substrate device of the invention that address the foregoing problem includes: on a substrate, a first conductive film; a first insulating film formed overlying the first conductive film; a second insulating film bonded on the first insulating film; a second conductive film overlying the second insulating film; and a contact hole opened in the first and second insulating films to connect the first conductive film and the conductive film, and penetrate a bonding interface between the first insulating film and the second insulating film. A point in the contact hole penetrating the bonding interface is not eroded by an etch solution.
According to the substrate device of the invention, electrical connection is provided, through the contact hole extending perpendicular to the substrate surface, between the interconnection, electrode, element or the like formed by the first conductive film and the interconnection, electrode, element or the like formed by the second conductive film, that are formed in the films sandwiching the bonding interface. Particularly, the point in the contact hole penetrating the bonding interface will not be eroded by an etch solution. Accordingly, this point is almost free of cracks or strip resulting from the etch solution. Reliable electric connection is available by the contact hole. Furthermore, reliable electrical connection or insulation is also available in the other interconnection, element or the like positioned close to that contact hole.
The above ultimately results in enhanced device reliability.
A substrate device in one form of the invention further includes a semiconductor layer on the second insulating film and an interlayer insulating film on the semiconductor layer, the second film being formed on the interlayer insulating film over the substrate, a channel region, a source region and a drain region being fabricated in the semiconductor layer to architect a thin film transistor, the contact hole being opened so as to penetrate through the interlayer insulating film, the second insulating film and the first insulating film.
In accordance ith this form, the thin film transistor is enhanced in performance by providing a single-crystal silicon layer as a semiconductor layer over the SOI substrate. Moreover, electrical connection is provided, through a contact hole almost free of defects, between the interconnection, electrode, element or the like formed by the second conductive film positioned above the thin film transistor and the interconnection, electrode, element or the like formed by the first conductive film positioned below the thin film transistor. Thus, entire device reliability is high.
In accordance with this form, the first conductive film is formed by a light shielding conductive film in a region of the semiconductor layer that is opposed to the channel region on the substrate.
In accordance with this structure, in the case of using a transparent substrate as a substrate, it is possible to favorably shield against the light incident on the channel region of the thin film transistor from the side of the substrate by the light shielding first conductive film. Due to this, the characteristic of the thin film transistor can be further enhanced by reducing or preventing the occurrence of light-leak current in the channel region due to a photoelectric effect.
In this case, it is advantageous to connect the first conductive film to a fixed-potential interconnection formed by the second conductive film through the contact hole, because the potential variation on the first conductive film having the light shielding property has no negative effect upon the thin film transistor.
Another form of a substrate device of the invention further includes, on the substrate, a pixel electrode, an intermediate conductive film interlevel-connecting the pixel electrode and one of the source region and the drain region. The substrate device also includes a pixel-potential capacitance electrode, and a capacitance line including a fixed-potential capacitance electrode arranged opposite to the pixel-potential capacitance electrode through a dielectric film. A storage capacitance is architected and connected from the pixel-potential capacitance electrode and the fixed-potential capacitance electrode to the pixel electrode.
In accordance with this form, the pixel electrode and one of the source and drain regions are interlevel-connected by an intermediate conductive film. Consequently, even where the interlayer distance is long between both structures, both structures can be favorably electrically connected together while avoiding the technical difficulty in connecting them through a long-distance contact hole or the like. Furthermore, the intermediate conductive film providing for such interlevel-connection also serves as a pixel-potential capacitance electrode of a storage capacitance. Accordingly, it is possible to simplify the overlying structure and manufacturing process as compared to the case of separately forming an interlevel-connecting conductive film and a pixel-potential capacitance electrode conductive film.
In this form, one of the intermediate conductive film and the capacitance line may be the same film as the second conductive film.
In accordance with this structure, using the same film as the second conductive film, the overlying structure and manufacturing process on the substrate can be simplified.
In the form architected with the storage capacitance, at least one of the intermediate conductive film and the capacitance line may be formed by a conductive light shielding film and include a portion covering the channel region at above thereof on the substrate.
In accordance with this structure, because the channel region is covered from above by at least one of the intermediate conductive film formed by a conductive light shielding film and the capacitance line, the channel region can be shielded against the incident light from above. Consequently, it is possible to effectively reduce or prevent, in the channel region, the occurrence of light-leak current due to a photoelectric effect resulting from incident light. Moreover, the overlying structure and manufacturing process can be simplified as compared to the case of separately forming such a light shielding film.
Incidentally, such a conductive light shielding film may be formed of a single metal, an alloy, a metal silicide, a polyside or a lamination thereof, including at least one of refractory metals, e.g., Ti, Cr, W, Ta and Mo. Otherwise, it may be formed of another metal, such as Al (aluminum).
The form architected with the storage capacitance further includes, on the substrate, a scanning line connected to a gate electrode formed on the channel region through a gate insulating film, a data line connected to the other of the source region and the drain region, and another intermediate conductive film interlevel-connecting between the data line and the other of the source region and the drain region and formed by the same film as the second conductive film.
In accordance with this structure, the data line and the other of the source and drain regions are interlevel-connected together by another intermediate conductive film. Consequently, even if the interlayer distance between both structures is long, favorable electrical connection is provided between the both while reducing or avoiding the technical difficulty in connecting both structures by a long-distance contact hole or the like. Furthermore, the overlying structure and manufacturing process on the substrate can be simplified by using, as the other intermediate conductive film, the same film as the second conductive film.
In this case, the storage capacitance may be partly provided at least in a region overlapped with the scanning line as viewed in a plan view.
In accordance with this structure, because a storage capacitance can be fabricated in a region overlapped with the scanning line, storage capacitance can be increased without narrowing the opening area in each pixel.
In this case, the storage capacitance may be partly provided at least in a region that is overlapped with the data line as viewed in a plan view.
In accordance with this structure, because a storage capacitance can be fabricated in a region that is overlapped with the data line, storage capacitance can be increased without narrowing the opening area in each pixel.
A method for manufacturing an electrooptical device of the invention that address the foregoing problem and that includes various of the above forms can also include: a step of bonding together the substrate device with a counter electrode in a oppositely arranged state, and a step of filling an electrooptical substance between the substrate device and the counter substrate.
This method can enhance the device reliability and manufacturing yield in an electrooptical device, such as a liquid-crystal device, utilizing the bonding or SOI technique.
An electrooptical device of the invention that address the foregoing problem and that includes various of the above forms can also include a counter substrate arranged opposite to the substrate device; and an electrooptical substance sandwiched between the counter substrate and the substrate device.
This electrooptical device of the invention can enhance device reliability.
An electrooptical device in one form of the invention includes a first interconnection or electrode formed by the first conductive film, and a second interconnection or electrode formed by the second conductive film, in a peripheral region positioned in a periphery of an image display region on the substrate arranged with the electrooptical substance, the contact hole connecting between the first interconnection or electrode and the second interconnection or electrode in the peripheral region.
In accordance with this structure, various interconnections, electrodes or thin film transistors can be structured by using the first and second conductive films in the image display region, while the first interconnection or electrode of the first conductive film and the second interconnection or electrode of the second conductive film are favorably connected together by using a contact hole in the peripheral region.
An electrooptical device in another form of the invention further includes a peripheral circuit fabricated in a peripheral region positioned in a periphery of an image display region on the substrate arranged with the electrooptical substance, the peripheral circuit including the first conductive film, the second conductive film and the contact hole.
In accordance with this form, various interconnections, electrodes or thin film transistors can be structured by using the first and second conductive films in the image display region while peripheral circuits can be structured by using the first and second conductive films and contact holes in the peripheral region.
An electronic appliance of the invention that is structured by having the foregoing electrooptical device of the invention can provide a reliable electronic appliance in various kinds, e.g., a projector, a display device incorporated in OA device equipment and a display device in cellular phone.
The operation and other advantages of the invention will be made apparent from the embodiments to be explained in the following.